I. Field of the Invention
The prior art includes numerous ventilators and ancillary equipment used in patient care. This equipment serves the vital purpose of supplying life sustaining oxygen to the patient's lungs. Many significant developments have been made in ventilator equipment since it was first introduced. Yet even the most sophisticated equipment available in the prior art suffers from one very significant problem, the accumulation of CO.sub.2 over time can greatly impair the health of a patient who would not be receiving treatment via a ventilator, but for the patient's already poor health.
II. Description of the Prior Art
The adverse effects of accumulation of carbon dioxide in the "dead spaces" of a ventilator or patient's airway have been known since the 1960's. Since that time, doctors have attempted to bypass the dead spaces of the mouth and upper airway by employing a tracheostomy. When a tracheostomy is employed, the air to be inhaled never passes through the mouth or upper airway where carbon dioxide can accumulate. More recently, a technique known as tracheal gas insufflation has been used to "flush" carbon dioxide from the dead spaces of the ventilator and the patient's airway.
Tracheal gas insufflation is the introduction of a low flow of oxygen or air into the endotracheal tube of a mechanically ventilated patient. The gas is directed through a small catheter or secondary pathway to the distal end of the endotracheal tube. This serves to introduce the oxygen or air just above the carina and flush the carbon dioxide from the endotracheal tube so the patient does not "rebreathe" the carbon dioxide with the next breath.
Traditionally, tracheal gas insufflation has been applied in a continuous flow manner. This has several disadvantages. First, the continuous flow dries out secretions making them difficult to remove. Second, continuous flow can dry mucosa resulting in tissue damage. Third, the additional gas flow adds to the desired tidal volume and end expiratory pressure making the ventilator settings inaccurate. Fourth, the additional gas flow increases the effort required for the patient to trigger the ventilator.